LOWER CRETACEOUS FOSSILS — ETHERIDGE. 145 



sigmoidal ; here and there one is bifurcate, the bifurcations 

 supra-dorsal in position. There is one row of pimple-like, uniform 

 tubercles, on either side the median line of the venter, along the 

 abdominal margins, one on each costa. 



The specimen agrees with C. leptus except in the bifurcation 

 of a few of the costa?, and the presence of the pimple-like 

 tubercles. 



Amongst the Port Darwin Cretaceous fossils of Shoal Bay 

 occurred a small Crioceras 28 whorl which may possibly be an 

 inner volution of this form, although the venter is subtruncate 

 instead of round, and a well-marked impressed zone is present. 

 Attention is mainly called to this with the view of future 

 identification. 



Loc. — Barcoo, Wai'd, and Nive Rivers District [A.M. (//. W. 

 Blomfield)J\ 



Crioceras jackii, Eth. fil. 



(Plate xxxi.; PL xxxii.,figs. 1, 2 and 3; PI. xxxiii.,fig. 1; Pl.xxxiv., 

 fig.l; PI. xxxv., fig. 1; PI. xxxvi., fig. 1; PI. xxxvii.; PI. 

 xxxviii., figs. 3-5.) 



Crioceras jackii, Eth. fil., Proc. R. Phys. Soc. Edinb., v., 1S80, 



p. 305, pi, xvii., figs. 55-58. 

 Crioceras irrequlare, Ten. Woods, Proc. Linn. Soc. N. S. Wales, 



xvi., 188*2, p. 151, pi. viii., f. 2. 

 Crioceras anslrale, Eth. til., Geol. Pal. Q'land, etc.. 1892, p. 499, 



pi. xxxi., f. 1; pi. xxxii., figs. 1-5. 

 Crioceras irregular e, Eth. fil., Geol. Pal. Q'land, etc.. 1892, 



p. 501, pl.xxxiii., f. 1; pi. xlii., f. 16. 



iSp. Chars. — Shell large, robust, whorls five or six, close coiled, 

 rapidly enlarging and overhanging one another; venter rounded 

 or convex, rapidly broadening as the shell grew; siphuncle small; 

 abdominal margins obtuse; dorsum more or less concave, costate; 

 impressed zone broad, shallow ; flanks convex ; umbilical cavity 

 wide and open ; section varies from octagonal round the full}' 

 tubercled costa? to transversely deltoid around the non-tubercled. 

 Sculpture varies at different stages of growth ; the first two and 

 a half to three whorls bear a series of prominent or thickened 

 obtuse costa? separated by from two to four (commonly two) 

 ordinary round small costa?, all close together; beyond the above 

 point costa? are all simple, regular and uniform, or a few bifurcate 



28 Etheridge— S. Austr. Pari. Papers (Suppl. to Xq. 55, 190G). 1007, p. 17, 

 pi. ix., figs. 7 and 8. 



